1. Field of the Invention
The present invention relates to a keyboard with separated keyboard frames and a portable computer system having the same, and more particularly to a keyboard having at least two separated keyboard frames with a key matrix assigned respectively thereto, which generates key scanning codes in response to key entries, and a portable computer having the same.
2. Description of the Related Art
In general, a keyboard is a major device for data entry, and has a plurality of keys to provide easy data entry. Typically, a keyboard has a keyboard frame, a key matrix connected thereto and a keyboard controller for managing the general operation of the keyboard. The keyboard controller, generally, consists of a microcomputer. The steps of processing key entry are as follows:
The keyboard controller periodically checks whether any key entry has taken place by scanning the key matrix. Once perceiving a key entry, the keyboard controller transfers a scanning code assigned to the pressed key to a computer system. That is, the keyboard controller generates a scanning signal (pulse signal) and provides it to an input of the key matrix and determines whether a key has been pressed by receiving the corresponding output from an output of the key matrix. A usual keyboard mounted on a portable computer is also operated in the same way as described above.
However, most of the above-mentioned keyboards have a single frame (or a single keypad) in its structure, which is not suitable for an input device, such as a keyboard for repeated key inputs. Especially, such a keyboard having a single frame is still less suitable for a portable computer. In the case of a personal desk top computer, in order to solve such a problem, a keyboard having several keyboard frames which are separated from each other is currently being used.
Such a keyboard includes first and second frames which are separated from each other and first and second matrices respectively assigned thereto. A matrix cable connects the first key matrix to the second key matrix and a keyboard controller. The operation of the keyboard having separate keyboard frames is performed in the same manner as a keyboard having a single keyboard frame. That is, the key controller generates scanning signals which are provided through the first key matrix to the second key matrix. The transfer of the scanning signals from one key matrix to the other key matrix is accomplished by the matrix cable connected therebetween. If there is a key entry through the first keyboard frame, a scanning code generated by the first keyboard frame is supplied through the matrix cable via the second key matrix to the keyboard controller. The keyboard controller then generates a key input signal corresponding to the entry key and the key input signals are serially transmitted to a microcomputer embodied in the computer system. Alternatively, if there is a key entry through the second keyboard frame, a scanning code generated by the second keyboard frame is supplied to the keyboard controller which generates a key input signal in the same manner as with the first keyboard frame.
In case of connecting such a keyboard to a portable computer, however, it is complicated to connect two separated key matrices to each other by using a matrix cable. Besides, it is difficult to locate a keyboard having a matrix cable within a limited space of a portable computer body. Since the keyboard also has a keyboard controller and several circuits, its structure is suitable for, for example, a desktop or tower computer system whose computer body is separated from the keyboard, but not for a portable computer system.
Specifically, since the keyboard has a keyboard controller consisting of a microprocessor or a microcomputer, the product cost thereof is relatively high, as compared to a keyboard which does not require a keyboard controller.
The patent to Margolin, U.S. Pat. No. 3,940,758, entitled EXPANDABLE KEYBOARD FOR ELECTRONIC POCKET CALCULATORS AND THE LIKE, discloses a keyboard having three frames 11-13 which are each separately connected to a computer circuit 20.
The patent to Morita et al., U.S. Pat. No 4,847,799, entitled KEYBOARD APPARATUS HAVING SEPARATE WORKING AREAS WITH THUMB-OPERATED SHIFTING OF KEY FUNCTIONS, discloses a keyboard having two frames which are both separately connected to a microprocessor 6 via an input port 5.
The patent to Okada, U.S. Pat. No. 5,208,638, entitled FACSIMILE APPARATUS, discloses a facsimile apparatus in which a ten-keypad and a plurality of one-touch keys are separately connected to a central processing unit via two respective interface units.
The patent to Vernon et al, U.S. Pat. No. 5,214,421, entitled AUTOMATIC KEYBOARD AND MONITOR SWITCHING DEVICE, discloses an arrangement in which two separate keyboards are alternatively connected to the central processing unit of a personal computer.
While each of the aforecited patents each disclose features in common with the present invention, none of these patents teach or suggest a keyboard having a plurality of keyboard frames and a plurality of key matrices respectively assigned thereto, as recited in the present claims, thereby obviating the need for a keyboard controller and a matrix cable for the keyboard.